N-Alkyl-2-[4-(trifluoromethyl)benzoyl]hydrazine-1-carboxamides and Their Analogues: Synthesis and Multitarget Biological Activity.

Based on the isosterism concept, we have designed and synthesized homologous N-alkyl-2-[4-(trifluoromethyl)benzoyl]hydrazine-1-carboxamides (from C1 to C18) as potential antimicrobial agents and enzyme inhibitors. They were obtained from 4-(trifluoromethyl)benzohydrazide by three synthetic approaches and characterized by spectral methods. The derivatives were screened for their inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) via Ellman's method. All the hydrazinecarboxamides revealed a moderate inhibition of both AChE and BuChE, with IC50 values of 27.04-106.75 µM and 58.01-277.48 µM, respectively. Some compounds exhibited lower IC50 for AChE than the clinically used drug rivastigmine. N-Tridecyl/pentadecyl-2-[4-(trifluoromethyl)benzoyl]hydrazine-1-carboxamides were identified as the most potent and selective inhibitors of AChE. For inhibition of BuChE, alkyl chain lengths from C5 to C7 are optimal substituents. Based on molecular docking study, the compounds may work as non-covalent inhibitors that are placed in a close proximity to the active site triad. The compounds were evaluated against Mycobacterium tuberculosis H37Rv and nontuberculous mycobacteria (M. avium, M. kansasii). Reflecting these results, we prepared additional analogues of the most active carboxamide (n-hexyl derivative 2f). N-Hexyl-5-[4-(trifluoromethyl)phenyl]-1,3,4-oxadiazol-2-amine (4) exhibited the lowest minimum inhibitory concentrations within this study (MIC ≥ 62.5 µM), however, this activity is mild. All the compounds avoided cytostatic properties on two eukaryotic cell lines (HepG2, MonoMac6).

Dibasic Derivatives of Phenylcarbamic Acid against Mycobacterial Strains: Old Drugs and New Tricks?

In order to provide a more detailed view on the structure⁻antimycobacterial activity relationship (SAR) of phenylcarbamic acid derivatives containing two centers of protonation, 1-[2-[({[2-/3-(alkoxy)phenyl]amino}carbonyl)oxy]-3-(dipropylammonio)propyl]pyrrolidinium oxalates (1a⁻d)/dichlorides (1e⁻h) as well as 1-[2-[({[2-/3-(alkoxy)phenyl]amino}carbonyl)oxy]-3-(di-propylammonio)propyl]azepanium oxalates (1i⁻l)/dichlorides (1m⁻p; alkoxy = butoxy to heptyloxy) were physicochemically characterized by estimation of their surface tension (γ; Traube's stalagmometric method), electronic features (log ε; UV/Vis spectrophotometry) and lipophilic properties (log kw; isocratic RP-HPLC) as well. The experimental log kw dataset was studied together with computational logarithms of partition coefficients (log P) generated by various methods based mainly on atomic or combined atomic and fragmental principles. Similarities and differences between the experimental and in silico lipophilicity descriptors were analyzed by unscaled principal component analysis (PCA). The in vitro activity of compounds 1a⁻p was inspected against Mycobacterium tuberculosis CNCTC My 331/88 (identical with H37Rv and ATCC 2794, respectively), M. tuberculosis H37Ra ATCC 25177, M. kansasii CNCTC My 235/80 (identical with ATCC 12478), the M. kansasii 6509/96 clinical isolate, M. kansasii DSM 44162, M. avium CNCTC My 330/80 (identical with ATCC 25291), M. smegmatis ATCC 700084 and M. marinum CAMP 5644, respectively. In vitro susceptibility of the mycobacteria to reference drugs isoniazid, ethambutol, ofloxacin or ciprofloxacin was tested as well. A very unique aspect of the research was that many compounds from the set 1a⁻p were highly efficient almost against all tested mycobacteria. The most promising derivatives showed MIC values varied from 1.9 µM to 8 µM, which were lower compared to those of used standards, especially if concerning ability to fight M. tuberculosis H37Ra ATCC 25177, M. kansasii DSM 44162 or M. avium CNCTC My 330/80. Current in vitro biological assays and systematic SAR studies based on PCA approach as well as fitting procedures, which were supported by relevant statistical descriptors, proved that the compounds 1a⁻p represented a very promising molecular framework for development of 'non-traditional' but effective antimycobacterial agents.

Synthesis and biological evolution of hydrazones derived from 4-(trifluoromethyl)benzohydrazide.

Reflecting the known biological activity of isoniazid-based hydrazones, seventeen hydrazones of 4-(trifluoromethyl)benzohydrazide as their bioisosters were synthesized from various benzaldehydes and aliphatic ketones. The compounds were screened for their in vitro activity against Mycobacterium tuberculosis, nontuberculous mycobacteria (M. avium, M. kansasii), bacterial and fungal strains. The most antimicrobial potent derivatives were also investigated for their cytostatic and cytotoxic properties against three cell lines. Camphor-based molecule, 4-(trifluoromethyl)-N'-(1,7,7-trimethylbicyclo[2.2.1]heptan-2-ylidene)benzohydrazide, exhibited the highest and selective inhibition of M. tuberculosis with the minimum inhibitory concentration (MIC) of 4 µM, while N'-(4-chlorobenzylidene)-4-(trifluoromethyl)benzohydrazide was found to be superior against M. kansasii (MIC = 16 µM). N'-(5-Chloro-2-hydroxybenzylidene)-4-(trifluoromethyl)benzohydrazide showed the lowest MIC values for gram-positive bacteria including methicillin-resistant Staphylococcus aureus as well as against two fungal strains of Candida glabrata and Trichophyton mentagrophytes within the range of ≤0.49-3.9 µM. The convenient substitution of benzylidene moiety at the position 4 or the presence of 5-chloro-2-hydroxybenzylidene scaffold concomitantly with a sufficient lipophilicity are essential for the noticeable antimicrobial activity. This 5-chlorosalicylidene derivative avoided any cytotoxicity on two mammalian cell cultures (HepG2, BMMΦ) up to the concentration of 100 µM, but it affected the growth of MonoMac6 cells.

Antimicrobial activity of rhodanine-3-acetic acid derivatives.

Twenty-four 2-(4-oxo-2-thioxothiazolidin-3-yl)acetic acid (rhodanine-3-acetic acid)-based amides, esters and 5-arylalkylidene derivatives were synthesized, characterized and evaluated as potential antimicrobial agents against a panel of bacteria, mycobacteria and fungi. All of the derivatives were active against mycobacteria. N-(4-Chlorophenyl)-2-[5-(2-hydroxybenzylidene)-4-oxo-2-thioxothiazolidin-3-yl]acetamide demonstrated the highest activity against Mycobacterium tuberculosis with minimum inhibitory concentrations (MIC) of 8-16µM. Non-tuberculous mycobacteria were the most susceptible to 2-[5-(2-hydroxybenzylidene)-4-oxo-2-thioxothiazolidin-3-yl]acetic acids (MIC values ⩾32µM). The highest antibacterial activity against Gram-positive bacteria including methicillin-resistant Staphylococcus aureus exhibited 4-(trifluoromethyl)phenyl 2-(4-oxo-2-thioxothiazolidin-3-yl)acetate (MIC⩾15.62µM). Several structure-activity relationships were identified. The activity against Gram-negative and fungal pathogens was marginal.

Novel salicylanilides from 4,5-dihalogenated salicylic acids: Synthesis, antimicrobial activity and cytotoxicity.

Salicylanilides have proved their activity against tuberculosis (TB). One weak electron-withdrawing substituent is favored at the salicylic part, specially Cl or Br atoms at positions 4 or 5. On the other hand, the antimycobacterial activity of salicylanilides is negatively affected when a strong electron-withdrawing substituent (NO2) is present at the same positions. Herein we describe the synthesis and characterization of novel salicylanilides possessing two weak electron-withdrawing groups (halogen atoms) at their salicylic part and compare their antitubercular activity with their monohalogenated analogues. All dihalogenated derivatives proved to possess antitubercular activity at a very narrow micromolar range (MIC=1-4µM), similar with their most active monohalogenated analogues. More importantly, the most active final molecules were further screened against multidrug resistant strains and found to inhibit their growth at the range of 0.5-4µM.

Development of water-soluble 3,5-dinitrophenyl tetrazole and oxadiazole antitubercular agents.

In this work, four series of tertiary amine-containing derivatives of 3,5-dinitrophenyl tetrazole and oxadiazole antitubercular agents were prepared, and their in vitro antimycobacterial effects were evaluated. We found that the studied compounds showed lipophilicity-dependent antimycobacterial activity. The N-benzylpiperazine derivatives, which had the highest lipophilicity among all of the series, showed the highest in vitro antimycobacterial activities against Mycobacterium tuberculosis CNCTC My 331/88 (H37Rv), comparable to those of the first-line drugs isoniazid and rifampicin. The presence of two tertiary amines in these N-benzylpiperazine derivatives enabled us to prepare water-soluble dihydrochloride salts, overcoming the serious drawback of previously described 3,5-dinitrophenyl tetrazole and oxadiazole lead compounds. The water-soluble 3,5-dinitrophenyl tetrazole and oxadiazole antitubercular agents described in this work are good candidates for further in vitro and in vivo pharmacokinetic and pharmacodynamic studies.

Synthesis of readily available fluorophenylalanine derivatives and investigation of their biological activity.

A series of thirty novel N-acetylated fluorophenylalanine-based aromatic amides and esters was synthesized using N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide or phosphorus trichloride in pyridine. They were characterized by spectral methods and screened against various microbes (Mycobacterium tuberculosis, non-tuberculous mycobacteria, other bacteria, fungi), for their inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) and cytotoxicity. All amino acids derivatives revealed a moderate inhibition of both cholinesterases with IC50 values for AChE and BChE of 57.88-130.75µM and 8.25-289.0µM, respectively. Some derivatives were comparable or superior to rivastigmine, an established drug. Phenyl 2-acetamido-3-(4-fluorophenyl)propanoate was identified as the selective and most potent inhibitor of BChE. The esterification and amidation of parent acids led to an improved BChE inhibition. The esters are better inhibitors of BChE than the amides. The introduction of NO2 and CH3 groups into aniline ring and CF3 moiety in phenol is translated into lower IC50 values. Seven compounds showed selectivity index higher than 10 for at least one cholinesterase. Especially the esters exhibited a mild activity against Gram-positive bacteria, mycobacteria and several fungal strains with minimum inhibitory concentrations starting from 125µM. The highest susceptibility was recorded for Trichophyton mentagrophytes fungus.

Design, Synthesis, and Biological Evaluation of Isothiosemicarbazones with Antimycobacterial Activity.

A series of benzaldehyde and salicylaldehyde-S-benzylisothiosemicarbazones was synthesized and tested against 12 different strains of mycobacteria, Gram-positive and Gram-negative bacteria, and the significant selectivity toward mycobacteria was proved. Twenty-eight derivatives were evaluated for the inhibition of isocitrate lyase, which is a key enzyme of the glyoxylate cycle necessary for latent tuberculosis infection, and their iron-chelating properties were investigated. Two derivatives, 5-bromosalicylaldehyde-S-(4-fluorobenzyl)-isothiosemicarbazone and salicylaldehyde-S-(4-bromobenzyl)-isothiosemicarbazone, influenced the isocitrate lyase activity and caused a better inhibition at 10 µmol/L than 3-nitropropionic acid, a standard inhibitor. The compounds were also found to act as exogenous chelators of iron, which is an obligate cofactor for many mycobacterial enzymes. Due to their low cytotoxicity, together with the activity against isocitrate lyase and the ability to sequester iron ions, the compounds belong to potential antibiotics with the main effect on mycobacteria.

Novel Sulfamethoxazole Ureas and Oxalamide as Potential Antimycobacterial Agents.

Infections caused by Mycobacterium tuberculosis (Mtb.) and nontuberculous mycobacteria (NTM) are considered to be a global health problem; current therapeutic options are limited. Sulfonamides have exhibited a wide range of biological activities including those against mycobacteria. Based on the activity of 4-(3-heptylureido)-N-(5-methylisoxazol-3-yl)benzenesulfonamide against NTM, we designed a series of homologous sulfamethoxazole-based n-alkyl ureas (C1-C12), as well as several related ureas and an oxalamide. Fifteen ureas and one oxalamide were synthesized by five synthetic procedures and characterized. They were screened for their activity against Mtb. and three NTM strains (M. avium, M. kansasii). All of them share antimycobacterial properties with minimum inhibitory concentration (MIC) values starting from 2 µM. The highest activity showed 4,4'-[carbonylbis(azanediyl)]bis[N-(5-methylisoxazol-3-yl)benzenesulfonamide] with MIC of 2-62.5 µM (i.e., 1.07-33.28 µg/mL). Among n-alkyl ureas, methyl group is optimal for the inhibition of both Mtb. and NTM. Generally, longer alkyls led to increased MIC values, heptyl being an exception for NTM. Some of the novel derivatives are superior to parent sulfamethoxazole. Several urea and oxalamide derivatives are promising antimycobacterial agents with low micromolar MIC values.

Sulfadiazine Salicylaldehyde-Based Schiff Bases: Synthesis, Antimicrobial Activity and Cytotoxicity.

The resistance among microbes has brought an urgent need for new drugs. Thus, we synthesized a series of Schiff bases derived from the sulfa drug sulfadiazine and various salicylaldehydes. The resulting 4-[(2-hydroxybenzylidene)amino]-N-(pyrimidin-2-yl)benzene-sulfonamides were characterized and evaluated against Gram-positive and Gram-negative bacteria, yeasts, moulds, Mycobacterium tuberculosis, nontuberculous mycobacteria (M. kansasii, M. avium) and their cytotoxicity was determined. Among bacteria, the genus Staphylococcus, including methicillin-resistant S. aureus, showed the highest susceptibility, with minimum inhibitory concentration values from 7.81 µM. The growth of Candida sp. and Trichophyton interdigitale was inhibited at concentrations starting from 1.95 µM. 4-[(2,5-Dihydroxybenzylidene)amino]-N-(pyrimidin-2-yl)-benzenesulfonamide was identified as the most selective Schiff base for these strains with no apparent cytotoxicity and a selectivity index higher than 16. With respect to M. tuberculosis and M. kansasii that were inhibited within the range of 8 to 250 µM, unsubstituted 4-[(2-hydroxy-benzylidene)amino]-N-(pyrimidin-2-yl)benzenesulfonamide meets the selectivity requirement. In general, dihalogenation of the salicylic moiety improved the antibacterial and antifungal activity but also increased the cytotoxicity, especially with an increasing atomic mass. Some derivatives offer more advantageous properties than the parent sulfadiazine, thus constituting promising hits for further antimicrobial drug development.

Synthesis and In Vitro Antimycobacterial Activity of Novel N-Arylpiperazines Containing an Ethane-1,2-diyl Connecting Chain.

Novel 1-(2-{3-/4-[(alkoxycarbonyl)amino]phenyl}-2-hydroxyethyl)-4-(2-fluorophenyl)-piperazin-1-ium chlorides (alkoxy = methoxy to butoxy; 8a-h) have been designed and synthesized through multistep reactions as a part of on-going research programme focused on finding new antimycobacterials. Lipophilic properties of these compounds were estimated by RP-HPLC using methanol/water mobile phases with a various volume fraction of the organic modifier. The log kw values, which were extrapolated from intercepts of a linear relationship between the logarithm of a retention factor k (log k) and volume fraction of a mobile phase modifier (ϕM), varied from 2.113 (compound 8e) to 2.930 (compound 8h) and indicated relatively high lipophilicity of these salts. Electronic properties of the molecules 8a-h were investigated by evaluation of their UV/Vis spectra. In a next phase of the research, the compounds 8a-h were in vitro screened against M. tuberculosis CNCTC My 331/88 (identical with H37Rv and ATCC 2794), M. kansasii CNCTC My 235/80 (identical with ATCC 12478), a M. kansasii 6 509/96 clinical isolate, M. avium CNCTC My 330/80 (identical with ATCC 25291) and M. avium intracellulare ATCC 13950, respectively, as well as against M. kansasii CIT11/06, M. avium subsp. paratuberculosis CIT03 and M. avium hominissuis CIT10/08 clinical isolates using isoniazid, ethambutol, ofloxacin, ciprofloxacin or pyrazinamide as reference drugs. The tested compounds 8a-h were found to be the most promising against M. tuberculosis; a MIC = 8 µM was observed for the most effective 1-(2-{4-[(butoxycarbonyl)amino]phen-ylphenyl}-2-hydroxyethyl)-4-(2-fluorophenyl)piperazin-1-ium chloride (8h). In addition, all of them showed low (insignificant) in vitro toxicity against a human monocytic leukemia THP-1 cell line, as observed LD50 values > 30 µM indicated. The structure-antimycobacterial activity relationships of the analyzed 8a-h series are also discussed.

Novel derivatives of nitro-substituted salicylic acids: Synthesis, antimicrobial activity and cytotoxicity.

Inspired by the high antituberculous activity of novel nitro-substituted derivatives and based on promising predicted ADMET properties we have synthesized a series of 33 salicylanilides containing nitro-group in their salicylic part and evaluated them for their in vitro antimycobacterial, antimicrobial and antifungal activities. The presence of nitro-group in position 4 of the salicylic acid was found to be beneficial and the resulting molecules exhibited minimum inhibitory concentrations (MICs) ranging from 2 to 32 µM against Mycobacterium tuberculosis. The best activity was found for 2-hydroxy-4-nitro-N-[4-(trifluoromethyl)phenyl]benzamide (MIC=2 µM). 4-Nitrosalicylanilides were also found to be active against all Staphylococcus species tested while for MRSA strain 2-hydroxy-4-nitro-N-[4-(trifluoromethyl)phenyl]benzamide's MIC was 0.98 µM. None of the nitrosalicylanilides was active against Enterococcus sp. J 14365/08 and no considerable activity was found against Gram-negative bacteria or fungi. The hepatotoxicity of all nitrosalicylanilides was found to be in the range of their MICs for HepG2 cells.

Synthesis and in vitro biological evaluation of 2-(phenylcarbamoyl)phenyl 4-substituted benzoates.

Based on the previously described antimicrobial activity of salicylanilide derivatives, we designed and synthesized novel 2-(phenylcarbamoyl)phenyl 4-substituted benzoates. The most active salicylanilides were selected for esterification by various 4-substituted benzoic acids. These compounds were evaluated in vitro against Mycobacterium tuberculosis, including multidrug-resistant strains, nontuberculous mycobacteria (Mycobacterium avium and Mycobacterium kansasii), and eight bacterial and fungal strains. We also investigated the cytostatic and cytotoxic actions of the esters. The minimum inhibitory concentrations (MICs) against mycobacteria ranged from 0.125 to 8µM. Interestingly, the drug-resistant strains exhibited the highest susceptibility without any cross-resistance with established drugs. 4-Bromo-2-[4-(trifluoromethyl)phenylcarbamoyl]phenyl 4-nitrobenzoate showed the most potent inhibition with MIC values ranging from 0.25 to 2µM. Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus, were inhibited by two derivatives with MIC values of at least 0.49µM, whereas Gram-negative bacteria and most of the tested fungi did not display any marked susceptibility. Benzoates exhibited no cytotoxicity at concentrations up to 50µM but most caused significant cytostasis with IC50 values lower than 10µM. Some cytotoxicity-based selectivity indexes for drug-susceptible and drug-resistant M. tuberculosis as well as Staphylococci were higher than 100. These values indicate that some of these derivatives are promising candidates for future research.

Synthesis and biological activity of new salicylanilide N,N-disubstituted carbamates and thiocarbamates.

The development of novel antimicrobial drugs represents a cutting edge research topic. In this study, 20 salicylanilide N,N-disubstituted carbamates and thiocarbamates were designed, synthesised and characterised by IR, (1)H NMR and (13)C NMR. The compounds were evaluated in vitro as potential antimicrobial agents against Mycobacterium tuberculosis and nontuberculous mycobacteria (Mycobacterium avium and Mycobacterium kansasii) as well as against eight bacterial and fungal strains. Additionally, we investigated the inhibitory effect of these compounds on mycobacterial isocitrate lyase and cellular toxicity. The minimum inhibitory concentrations (MICs) against mycobacteria were from 4 µM for thiocarbamates and from 16 µM for carbamates. Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus, were inhibited with MICs from 0.49 µM by thiocarbamates, whilst Gram-negative bacteria and most of the fungi did not display any significant susceptibility. All (thio)carbamates mildly inhibited isocitrate lyase (up to 22%) at a concentration of 10 µM. The (thio)carbamoylation of the parent salicylanilides led to considerably decreased cytotoxicity and thus improved the selectivity indices (up to 175). These values indicate that some derivatives are attractive candidates for future research.

Salicylanilide diethyl phosphates: synthesis, antimicrobial activity and cytotoxicity.

A series of 27 salicylanilide diethyl phosphates was prepared as a part of our on-going search for new antimicrobial active drugs. All compounds exhibited in vitro activity against Mycobacterium tuberculosis, Mycobacterium kansasii and Mycobacterium avium strains, with minimum inhibitory concentration (MIC) values of 0.5-62.5µmol/L. Selected salicylanilide diethyl phosphates also inhibit multidrug-resistant tuberculous strains at the concentration of 1µmol/L. Salicylanilide diethyl phosphates also exhibited mostly the activity against Gram-positive bacteria (MICs ≥1.95µmol/L), whereas their antifungal activity is significantly lower. The IC50 values for Hep G2 cells were within the range of 1.56-33.82µmol/L, but there is no direct correlation with MICs for mycobacteria.

Synthesis and biological activity of quaternary ammonium salt-type agents containing cholesterol and terpenes.

New quaternary ammonium salt-type compounds with lipophilic cholesterol and terpene moieties were synthesized. The compounds showed promising antibacterial and antimycobacterial activities. Those compounds containing the cholesterol moiety showed significant activity against Staphylococcus aureus, Staphylococcus epidermidis, and Enterococcus faecium. On the contrary, the antimycobacterial activity increased with the presence of the terpene unit in the molecule.

Synthesis and antimycobacterial and photosynthesis-inhibiting evaluation of 2-[(E)-2-substituted-ethenyl]-1,3-benzoxazoles.

A series of twelve 2-[(E)-2-substituted-ethenyl]-1,3-benzoxazoles was designed. All the synthesized compounds were tested against three mycobacterial strains. The compounds were also evaluated for their ability to inhibit photosynthetic electron transport (PET) in spinach (Spinacia oleracea L.) chloroplasts. 2-[(E)-2-(4-Methoxyphenyl)ethenyl]-1,3-benzoxazole, 2-[(E)-2-(2,3-dihydro-1-benzofuran-5-yl)ethenyl]-1,3-benzoxazole and 2-{(E)-2-[4-(methylsulfanyl)phenyl]ethenyl}-1,3-benzoxazole showed the highest activity against M. tuberculosis, M. kansasii, and M. avium, and they demonstrated significantly higher activity against M. avium and M. kansasii than isoniazid. The PET-inhibiting activity of the most active ortho-substituted compound 2-[(E)-2-(2-methoxyphenyl)ethenyl]-1,3-benzoxazole was IC50 = 76.3 µmol/L, while the PET-inhibiting activity of para-substituted compounds was significantly lower. The site of inhibitory action of tested compounds is situated on the donor side of photosystem II. The structure-activity relationships are discussed.

N-substituted 2-isonicotinoylhydrazinecarboxamides--new antimycobacterial active molecules.

This report presents a new modification of the isoniazid (INH) structure linked with different anilines via a carbonyl group obtained by two synthetic procedures and with N-substituted 5-(pyridine-4-yl)-1,3,4-oxadiazole-2-amines prepared by their cyclisation. All synthesised derivatives were characterised by IR, NMR, MS and elemental analyses and were evaluated in vitro for their antimycobacterial activity against Mycobacterium tuberculosis H37Rv, Mycobacterium avium 330/88, Mycobacterium kansasii 235/80 and one clinical isolated strain of M. kansasii 6509/96. 2-Isonicotinoyl-N-(4-octylphenyl)hydrazinecarboxamide displayed an in vitro efficacy comparable to that of INH for M. tuberculosis with minimum inhibitory concentrations (MICs) of 1-2 µM. Among the halogenated derivatives, the best anti-tuberculosis activity was found for 2-isonicotinoyl-N-(2,4,6-trichlorophenyl)hydrazinecarboxamide (MIC=4 µM). In silico modelling on the enoyl-acyl carrier protein reductase InhA confirmed that longer alkyl substituents are advantageous for the interactions and affinity to InhA. Most of the hydrazinecarboxamides, especially those derived from 4-alkylanilines, exhibited significant activity against INH-resistant nontuberculous mycobacteria.

Diethyl 2-(phenylcarbamoyl)phenyl phosphorothioates: synthesis, antimycobacterial activity and cholinesterase inhibition.

A new series of 27 diethyl 2-(phenylcarbamoyl)phenyl phosphorothioates (thiophosphates) was synthesized, characterized by NMR, IR and CHN analyses and evaluated against Mycobacterium tuberculosis H37Rv, Mycobacterium avium and two strains of Mycobacterium kansasii. The best activity against M. tuberculosis was found for O-{4-bromo-2-[(3,4-dichlorophenyl)carbamoyl]phenyl} O,O-diethyl phosphorothioate (minimum inhibitory concentration of 4 µM). The highest activity against nontuberculous mycobacteria was exhibited by O-(5-chloro-2-{[4-(trifluoromethyl)phenyl]carbamoyl}-phenyl) O,O-diethyl phosphorothioate with MIC values from 16 µM. Prepared thiophosphates were also evaluated against acetylcholinesterase from electric eel and butyrylcholinesterase from equine serum. Their inhibitory activity was compared to that of the known cholinesterases inhibitors galanthamine and rivastigmine. All tested compounds showed a higher (for AChE inhibition) and comparable (for BChE inhibition) activity to that of rivastigmine, with IC50s within the 8.04 to 20.2 µM range.

Both Nitro Groups Are Essential for High Antitubercular Activity of 3,5-Dinitrobenzylsulfanyl Tetrazoles and 1,3,4-Oxadiazoles through the Deazaflavin-Dependent Nitroreductase Activation Pathway.

3,5-Dinitrobenzylsulfanyl tetrazoles and 1,3,4-oxadiazoles, previously identified as having high in vitro activities against both replicating and nonreplicating mycobacteria and favorable cytotoxicity and genotoxicity profiles were investigated. First we demonstrated that these compounds act in a deazaflavin-dependent nitroreduction pathway and thus require a nitro group for their activity. Second, we confirmed the necessity of both nitro groups for antimycobacterial activity through extensive structure-activity relationship studies using 32 structural types of analogues, each in a five-membered series. Only the analogues with shifted nitro groups, namely, 2,5-dinitrobenzylsulfanyl oxadiazoles and tetrazoles, maintained high antimycobacterial activity but in this case mainly as a result of DprE1 inhibition. However, these analogues also showed increased toxicity to the mammalian cell line. Thus, both nitro groups in 3,5-dinitrobenzylsulfanyl-containing antimycobacterial agents remain essential for their high efficacy, and further efforts should be directed at finding ways to address the possible toxicity and solubility issues, for example, by targeted delivery.